Millifluidic Lab-on-a-Chip technology for automated toxicity tests using the marine amphipod Allorchestes compressa

Amphipods have gained popularity as excellent bioindicators. They are important links in numerous food chains and have localized behavior that can be used to assess sediment toxicity and water quality. Bioassays performed with amphipods, however, largely still use 10–42 d static tests in large volumes, require manual manipulation of samples, and employ mortality, growth and reproduction as the major test criteria, which are time and labour intensive, and can be subject to "observer bias". This work describes design and validation of a miniaturized, continuous perfusion based Lab-on-a-Chip technology for automated sub-lethal behavioral toxicity tests using the native Australian marine amphipod Allorchestes compressa. An automation module with a high-resolution USB camera, user-friendly fluidic interconnects and miniaturized 3D-printed interface was developed. To evaluate performance of the new chip-based system, median lethal concentrations (LC50) of a panel of reference toxicants obtained on this system were compared with those from tests using conventional static protocols, and were not significantly different. Automated behavioral tests were then conducted by perfusing toxicants through the chip-based device to dynamically assess the effect of toxicants on selected locomotory parameters. Results showed that the system was able to detect and automatically analyse data to assess changes in the swimming behavior of A.compressa at toxicant concentrations that did not induce mortality in test populations. For the majority of chemical stressors tested, behavioral sub-lethal changes occurred early and in a concentration- and exposure time-dependent manner and could be recorded with no "observer" input. We postulate that integrated Lab-on-a-Chip systems can enable new avenues for "Early Warning" biomonitoring systems that can automate the use of sensitive behavioral indices to rapidly detect presence of toxicants in aquifers.